The confirmed scope was narrower than the old headline
Twitch's October 15, 2021 security update said the exposed material primarily included documents from its source-code repository and a subset of creator payout data. It stated that Twitch passwords had not been exposed. That is materially different from saying the service's entire data, including every user's credentials, had leaked.
Source [1]Stream keys and passwords serve different purposes
The same incident record said Twitch reset stream keys as a precaution on October 7. A stream key authorizes broadcasting software to send a stream; it is different from an account password. Some broadcasting setups required a manual replacement while others handled the change automatically.
This is the history of that response, not a new breach alert. For a current security incident, follow the service's current instructions and use its genuine account controls rather than links supplied by an unsolicited message. The WhatsApp multi-device guide offers related background on how account access can extend across several devices without making every credential interchangeable.
Source [1]